Syncopation shifts the accents of a rhythm away from where the listener expects them. In a bar of 4/4 counted “1 and 2 and 3 and 4 and”, the strong points are the numbers, especially 1 and 3. A syncopated rhythm stresses an “and”, leaves a rest where a strong beat should be, or holds a note over from a weak beat across a strong one. The ear feels a pull back towards the regular pulse, and that tension creates momentum.
Syncopation is found in much folk-dance music and in Western written music from the fourteenth century onwards, but it is one of the defining elements of jazz. In jazz lo-fi it appears in kick drums placed just before the beat, in chord stabs that land on an off-beat and in sampled horn phrases that start a fraction early, all of which keep a slow, simple loop from sounding mechanical.